What is algal bloom?
Algal bloom refers to the accumulation of algae or the rapid increase in the algae population in an aquatic system. They are usually green but there are others which are yellow-brown or red. The coloring usually depends on the algae species. They can be found in both marine and fresh waters and they cause discoloration of the water. This is one way that they can be recognized (Nancy, 2009). Algal bloom usually occurs due to high concentration of nutrients in the water and especially phosphorus (Lathrop et al, 1998). Generally most algae species are not harmful but Karenia brevis which is a quick grower and makes the water appear red is a harmful bloom. It is also called the red tide because of turning the water red
What is a harmful algal bloom?
A harmful algal bloom (HAB) is one that has negative effects on other living organisms through toxins production or by causing mechanical damage to other living organisms. The toxins that they produce are called brevetoxions and are known to have killed millions of marine fish and other marine organisms.
What causes HAB?
The specific causes of harmful algal bloom is unclear because they occur entirely naturally in some areas while in some locations, they seem to occur because of human activities. In other areas they seem to occur due to movement of ocean currents. Though the growth of HABs depends on the amount of nutrients in the water, different HABs have different environmental requirements for growth.
What are some of these harmful effects on the marine environment?
Their effect on the marine environment depends on the species involved. They produce brevetoxions which are neurotoxins that kill fish (Landsberg, 2002). The dead fish may be a source of other harmful Bacteria and this makes the marine environment to be contaminated (Gregg and Pamela)
What are the impacts on the public health?
The neurotoxins produced may accumulate in the tissues of the fish especially shell fish that feed on these harmful algae blooms. When people feed on these fish, they suffer from neurotoxin shell poisoning. This causes severe gastrointestinal and neurological symptoms that may include tingling fingers or toes (Bartram et al 1999)
What is the effect of red tide on the respiratory system?
People experience respiratory irritation of the eyes, nose and throat hence causing coughing, sneezing, wheezing, shortness of breath and tearing .This occurs when the wind containing the toxins blows onshore. People suffering from respiratory conditions like emphysema or asthma should avoid red tide areas. This is because they may experience these symptoms more severely (Sellner et al 2003). But in general, the symptoms are usually temporary and they disappear after a few hours when one is no longer exposed.
How safe is it to swim during a red tide?
It is usually very safe to swim during a red tide to most people. But to some, it may cause skin irritation and a burning in the eyes. Thus it will depend on ones susceptability.those people who are more vulnerable to irritation from other things e.g. plant products should avoid swimming in these waters (Van Dolah, 2000). Once irritation occurs when you are in the water, you should wash yourself thoroughly. Even though, one should not swim in waters containing dead fish as one may be infected with harmful bacteria.
Is it safe to eat shellfish from a red tide?
It is not recommendable to eat shell fish from a red tide because they are not safe (Red Tide FAQ). Neither is it safe to eat clams and oysters. This is because the neurotoxin is not destroyed by cooking (Song et al 2005) However; one can eat edible parts of crabs, shrimp, and lobsters because these are not affected by the toxins. Also one can eat the muscles of scallop but not the whole animal. Eating of dead animals in a red tide zone should be highly discouraged (Trainer et al 2000)
List of references
Bartram, J.; Wayne W. Carmichael, Ingrid Chorus, Gary Jones, and Olav M. Skulberg (1999). "Chapter 1. Introduction" Toxic Cyanobacteria in Water: A guide to their public health consequences, monitoring and management. World Health Organization http://www.who.int/water_sanitation_health/resourcesquality/toxicyanbact/en/Retrieved 2010-02-09.
Florida Fish and Wildlife Research Institute. "Red Tide Current Status Statewide Information" research.myfwc.com. http://research.myfwc.com/features/view_article.asp?id=9670 Retrieved 2010-02-09.
Gregg W, Pamela D. "Red Tides: Questions and Answers” U.S. Government. http://www.whoi.edu/fileserver.do?id=47320&pt=10&p=18553. Retrieved 2010-02-09.
Nancy, D. (May 2009). "Phytoplankton Blooms: The Basics” PDF. NOAA. http://floridakeys.noaa.gov/pdfs/wqpb.pdf Retrieved 2010-02-09.
"Harmful Algal Blooms: Red Tide: Home" www.cdc.gov. http://www.cdc.gov/hab/redtide/. Retrieved 2010-02-09.
Landsberg, J (2002). “The effects of harmful algal blooms on aquatic organisms”. Reviews in Fisheries Science, 10(2): 113-390 (2002)
Lathrop, C, Stephen R, John C, Patricia A., & Craig A. (May 1, 1998). "Phosphorus loading reductions needed to control blue-green algal blooms in Lake Mendota” Canadian Journal of Fisheries and Aquatic Sciences (Toronto, Ontario, Canada: National Research Council of Canada) 55 (5): 1169-1178. Retrieved February 09, 2010.
Lam CWY, Ho KC (1989). Red tides in Tolo Harbor, Hong Kong. In: Okaichi T, Anderson DM, Nemoto T (Eds) Red tides. Biology, environmental science and toxicology. Elsevier, New York, pp 49-52.
"Red Tide FAQ - Is it safe to eat oysters during a red tide?" www.tpwd.state.tx.us. http://www.tpwd.state.tx.us/landwater/water/environconcerns/hab/redtide/faq.phtml#q9Retrieved 2010-02-09
"Red Tide Index". www.tpwd.state.tx.us. http://www.tpwd.state.tx.us/landwater/water/environconcerns/hab/redtide/.Retrieved 2010-02-09.
"Red Tide Fact Sheet - Red Tide (Paralytic Shellfish Poisoning)". www.mass.gov. http://www.mass.gov/?pageID=eohhs2modulechunk&L=4&L0=Home&L1=Provider&L2=Guidance+for+Businesses&L3=Food+Safety&sid=Eeohhs2&b=terminalcontent&f=dph_environmental_foodsafety_p_red_tide&csid=Eeohhs2 .Retrieved 2010-02-09.
Sellner, G.; Doucette G., and Kirkpatrick J. (2003). "Harmful Algal blooms: causes, impacts and detection". Journal of Industrial Microbiology and Biotechnology 30 (7): 383-406. http://www.springerlink.com/content/ptybc0qg8y4klr5c/
Song, W.; Teshiba T., Rein K., and O'Shea K. E. (2005). "Ultrasonically induced degradation and detoxification of microcystin-LR (cyanobacterial toxin)". Environmental Science & Technology 39 (16): 6300-6305. http://www.greenpeace.org/china/en/news/fertiliser-algae-taihu
Trainer V, Adams G, Bill BD, Stehr CM, Wekell JC, Moeller P, Busman M, Woodruff D (2000) Domoic acid production near California coastal upwelling zones, June (1998). Limnol Oceanography. 45:1818-1833
Van Dolah, F.M. (2000). "Marine Algal Toxins: Origins, Health Effects, and Their Increased Occurrence”. Environmental Health Perspectives 108 (suppl.1): 133-141..